The present invention relates generally to electrical lamp fixtures used for growing plants, and specifically to an improved light emitting diode (LED) grow light apparatus, incorporating an extended point source LED array, preferably composed of LEDs of multiple wavelengths.
Typical grow lights make use of either metal halide (MH) incandescent bulbs, high pressure sodium (HPS) incandescent bulbs, or in some cases fluorescent bulbs. These broad-spectrum light sources are inefficient in producing light energy for the purpose of plant growth. In the case of fluorescent grow lights, the conversion of electrical energy into light energy is reasonably efficient, but the spectral content of the light energy is such that much of it is effectively wasted, and does not contribute to plant growth.
Metal halide and high pressure sodium bulbs can provide a very bright, intense light, but are also inefficient, both in terms of their conversion of electrical energy to light energy, and also in terms of spectral content. Furthermore, MH and HPS lights may generate wavelengths that are potentially harmful to plants. In particular, they product large amounts of radiated infrared (IR) energy, which can result in heat damage to plants. For this reason, MH and HPS lights may need to be mounted at some minimum distance above the plants, to avoid heat damage, thereby limiting their usefulness and mounting flexibility.
LED grow lights in general offer several advantages when used to grow plants. The conversion of electrical energy to light energy by LEDs is generally efficient, especially when compared to incandescent bulbs such as MH and HPS bulbs.
Another general advantage of LED grow lights is that the light from LEDs is partially directional, in contrast to the light that is emitted from broadband incandescent (MH and HPS) and fluorescent light sources. In particular, the light from LEDs is primarily emitted from the “top” surface of an LED chip. This lends itself to simpler reflector designs.
The primary historical disadvantage of existing and prior art LED grow lights has been their relative lack of total light output, especially when compared to MH and HPS grow lights, which are available as 400-1,000 Watt fixtures. Research in LEDs and solid-state lighting has resulted in the development of high brightness LEDs that efficiently produce relatively larger levels of light output, at higher electrical current levels. This has largely been achieved via advances in drawing heat away from the active junction of the LED, thereby allowing the LED to safely operate at these higher current levels. The electrical-to-optical conversion efficiency of LEDs is also being improved over time. However, in order to provide a sufficient total light output, most prior art LED grow lights require large numbers of LEDs, which are typically spaced widely apart in order to deal with the resultant heat dissipation issues. The spacing between adjacent LED chips in prior art LED grow lights is therefore several inches, or more. This negates much of the potential size and cost advantages of an LED grow light. In order to achieve the light output of 20 or more LED chips, the surface area of the prior-art LED grow light must be large. Also, each of the widely-spaced LED chips requires individual separate packaging, separate heat-sinking, and separate optics, thereby adding significantly to the size and cost of the grow light.